Glenn Miller - At Last!

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5/13/10

Alternators for your Classic!

A question was asked if you can wire your new alternator to the stock 30 - 35 amp guage in the dash. If the guage pegs at 30 amps and your running a higher amperage alternator, say a 60 or 75 amp; it should work fine. You risk damaging the amp guage, but that would be over along period of time.

I have wired into stock guages, like my 59 Buick, and it works. I run a 75 amp 3-wire alternator (which is better than a 1 wire), including an alternator lamp on the dash as well to give indication if the alternator fails, or if you loose a belt.

I have done other 58 and 59 models this way, it works for indicator purposes.

If you have a 105 amp alternator (which is extreme overkill if your running stock components, makes no logical sense), dont run it thought the amp guage, it will destroy it. Run an aftermarket unit or improvise a similar gauge to the stock guage panel. There are several threads of this done.

In case you ask why I use a 3 wire...it give 'pure' power/amps unlike a 1 wire. The 3 wire has your charging lead, a sensing lead and the indicator. The sensing lead senses what is in the battery and tells the alternator how much to charge, and at what volts. Typically an alternator should give between 13.8 to 14.4 volts to the battery during its charging cycle. Depending on the length of the cable from the alt to the battery, you get a voltage drop. The sensing lead tells the alt to add more if needed. Say you have a 2 volt loss from the alt to the battery. It boosts it charge to 15.8 - 16.4 for a pure 12 volt charge at the battery.

The 1 wire, gives 13.8 - 14.4, that's it, you get a 2 volt loss down the charging feed wire, your alt does not boost to make up the difference...so it works harder. Yeah it an easy hook up, but not as efficient.

A great all around 3 wire is one for 1983 Chevy Cavalier. It uses a 12SI GM alternator. 75-95 amps charging. It has the high air efficient fan with v groove. For 40 - 63 amp charging, you can step down to a 10SI alternator from a 1978 Oldsmobile Cutlass Supreme.

Most high amp 1 wire alternators, have the typical air cooling fan (metal blades), not enough air flow to keep it cool, you get burn out faster. Thus why I dont like em.

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